Piston



Jan. 4, 1938. NELSON 2,104,350

PISTON Filed July 28, 1926 2 Sheets-Sheet 1 Jan. 4, 1938. A. L. NELSON PISTON Filed July 28, 1926 2 Sheets-Sheet 2 f I wmtoz 951311; em

Patented Jan. 4, 1938 PATENT OFFICE PISTON Adolph L. Nelson, Detroit, Mich, assignor to Bohn Aluminum& Brass Corporation, Detroit,

Mich.

Application July 28, 1926, Serial No. 125,339

6 Claims.

This invention relates to pistons and aims particularly to improve the construction of pistons formed of light weight metal.

One of the objects of the invention is to provide a piston in which the upper part of the skirt is insulated from the head while the lower part of the skirt is connected to the head in a manner to provide an effective heat path from the head to the lower part of the skirt. The piers connecting the head to the skirt are reinforced by a plurality of columns which act to reinforce the piers and increase the capacity of the heat path from the head to the skirt.

The invention also includes spacing means formed of insulating material having a low rate of thermal expansion and used to support the upper part of the skirt and to determine the rate of expansion thereof.

'A further object is to so construct the lower part of the skirt that it will be influenced by the control member located in the upper part of the skirt.

While a preferred embodiment has been disclosed for purposes of illustration, it should be understood that various changes may be made in the structure without departing from the spirit and scope of the invention as hereinafter set forth and claimed.

In the drawings: Fig. 1 is an elevation of a piston embodying the invention;

Fig. 2 is an elevation; partly broken away, looking from the right of Fig. 1;

Fig. 3 is a section taken on line 3-3 of Fig. 2; Fig. 4 is a section taken on line 4-4 of Fig. 1; Fig.5 is an elevation corresponding to Fig. 2 and showing a modification;

Fig. 6 is a section on line 6 6 of Fig. 5. Referring to the drawings more specifically. the piston, which is preferably formed of light weight material such as aluminum alloy, comprises a head I0 and a skirt II. The upper part of the skirt is insulated from the head in any desired manner, as by providing an air gap between 5 these parts as shown in the drawings. Piers I2 extend downwardly from the head In into cut-outs l3 formed in opposite sides of the skirt. The piers, which carry the pin bosses I4, are extended below the pin bosses and are joined to arcuate ribs l5 which are connected to the lower circular part of the skirt.

The sides of the skirt lying at right angles to the pin bosses constitute the thrust faces l6 and II. The upper ends of the thrust faces, which 7.5 are separated from the head and are not supported by adjacent parts of the skirt, are held in place by spacing means shown in the form of struts l8. The struts, which are imbedded in the piers l2 above the axis of the pin bosses andhave their ends secured to the thrust faces, are formed 5 of any material having a relatively low coefiicient .of expansion, such as certain alloy steels. Since the upper ends of the thrust faces have no direct lateral connection with the rest of the skirt or with the piers except through the struts, it will 10 be clear that the diametrical expansion through this part of the skirt will be determined largely by the struts. It is advisable to select a strut material which has a low coefiicient of thermal conductivity as well as a low coeificient of expan- 15 sion. A material filling both of these requireinents is found in a nickel-iron alloy such as Invar. By forming the struts of such a material the upper ends of the thrust faces will be rigidly braced and controlled and will at the same 20 time remain relatively cool because they are insulated from the piston head.

In a piston constructed in the above manner the expansion of the top of the skirt across the thrust faces is efficiently controlled and the upper 25 ends of the thrust faces are held in proper hearing relation to the cylinder wall. In some cases it is advisable to place a slot IS in the thrust face I6 in a position opposite and between the struts.

The part of the skirt below the cut-outs I3 30 forms a complete circle as shown in Fig. 4. The parts of this circle under the bosses are braced and reinforced by the horizontal arcuate ribs l5 which are integral with the piers l2 and with the skirt. The upper end of each pier is strengthened and augmented by a central column 2|], which is disposed partly on the inside and partly on the outside of the pier, and by interior side columns 2|. This structure provides a direct and efilcient path by which heat can travel from the 40 head into the lower part of the skirt, which comes in contact with the cooled cylinder wall. The upper parts of the thrust faces are free of any direct (straight-line) connection with the head or piers except that furnished by the struts. only other connection between the upper part of each thrust face and the head is the indirect connection by way of the lower circular part and the pier.

In the piston disclosed the lower part of the 50 skirt is formed with a series of overlapping slots so arranged in relation to the thrust faces and the bracing ribs that the thrust faces are not materially weakened and the skirt maintains its circular shape, while at the same time this part The 5' of the skirt is able to yield to the influence of the struts I8. This result is obtained by cutting a slot 22 below each pin boss and extending from the lower edge of the skirt upwardly toward the rib I5. A pair of closed-end slots 23 are formed in the thrust face l1. Each of the slots 23 extends longitudinally of the thrust face in the vicinity of one end of a rib l5, and is centered relative to the'rib.

The modification of Figs. 5 and 6 is substantially similar to that already disclosed except that the ribs l5 are disposed vertically instead of horizontally. The central part of each rib is separated from the lower rim of the skirt by an ,opening 24 which is met by the slot 21 to form a T-shaped aperture. The slots 23' are centered with relation to the'ends of the ribs l5.

I claim:--

1. A piston comprising a head and a skirt, pin bosses connected to the head, the skirt having thrust faces between the pin bosses, ribs connecting the lower part of the pin bosses to the skirt, the skirt having a slot formed therein below one of the ribs, and having also a pair of closed-end slots formed in one of the thrust faces in the zone of the ribs. i

2. A piston comprising a head and a skirt, pin bosses connected to the head, the skirt having thrust faces between the pin bosses, ribs connecting the lower part of the pin bosses to the skirt, the skirt having a slot formed therein, below each of the ribs, and having also a pairof closed-end slots formed in one of the thrust faces in the zone of the ribs.

3. A piston comprising a head, piers depending from the head and carrying pin bosses, a skirt having thrust faces between the pin bosses and having their upper parts insulated from the piston head, a strut of insulating and inexpansible material buried in each pier and secured to the upper part of the thrust faces, ribs connecting the lower part of the pin bosses to the skirt, the skirt having a slot extending upwardly into the skirt below each rib and a pair of closed-end slots formed in one of the thrust faces in the zone of the ribs.

4. A piston comprising a head, piers depending from the head and carrying pin bosses, a skirt having thrust faces between the pin bosses and having their upper parts insulated from the piston head, a strut of insulating and inexpansible material buried in each pier and secured to the upper part of the thrust faces, the skirt having a slot formed in one of the thrust faces in the plane of the struts, ribs connecting the lower part of the pin bosses to the skirt, the skirt being formed with a slot extending upwardly into the skirt below each rib and a pair of closed-end slots formed in the other thrust face in the zone of the ribs.

5. A piston comprising a head and a skirt, pin bosses connected to the head, the skirt having thrust faces between the pin' bosses, ribs connecting the lower part of the pin bosses to the skirt, the lower part of each rib being separated from the skirt by an aperture, the skirt having a slot extending from the lower edge of the skirt to the aperture and a pair of closed-end slots formed in one of the thrust faces in the zone of the ribs.

6. A piston comprising a head and a skirt, piers depending from the head and carrying piston pin bosses, the skirt having thrust faces between the pin bosses, ribs extending laterally from the piers to the skirt, the ribs being homogeneous with the piers and with the skirt, the skirt being formed with a pair of closed-end slots formed in one of the thrust faces in thezone of the ribs.

ADOLPH L. NELSON. 

